periods while on nexplanon

hey guys, I'm new to this. my husband and I decided that we wanted to wait to have kids so I got the nexplanon. I now have had it for a month. my doctor said it would probably mess up my period. it sure did! I have now been bleeding for almost 14 days where my normal period would probably be only 5 days. some of it has been normal bleeding, while other days it's been spotting with pretty dark blood. anybody have experience with this? should I be concerned at all?

just wondering! like I said, I am new to this! :)

thanks!